Research On New Fiber High Energy Ultrashort Pulse Light Sources

High energy femtosecond light fiber pulse sources have been extensively applied in optical communication, bioscience, and laser technology and so on. Nowadays, mode-locking technology is the main way to obtain femtosecond pulse. According to cavity dispersion, mode-lock fiber laser can be divided into siliton pulse fiber laser, stretched pulse fiber laser, normal dispersion fiber laser and so on. One can obtain the pulse with highest energy by using the technology of reshape dissipative soliton in normal dispersion regime. In order to produce femtosecond pulse with higher energy, people often need amplify the seed pulse in a fiber amplifier system, then they should compress the pulse in a grating. Using this method one need propagate the seed pulse self-similarly in amplifier before into the compressor. In recent years, it was found that highly chirped parabolic pulse can be produced in a self-similar laser. In this thesis, we theoretically and experimentally study research on new high energy fiber ultrashort pulse light sources. The main contents are as follows:1. We have theoretically obtained the generalized nonlinear Schr?dinger equation that governs propagation of optical pulse in fiber. We also introduced the standard split-step Fourier method used to solve the pulse propagation equations.2. We have experimentally observed parabolic pulses with large chirp in a normal dispersion fiber laser. The pulse duration is 3.29 ps, the 3 dB spectrum width is ~ 60.0 nm and the center wavelength is about 1550 nm, so the time bandwidth product is 24.6. By increasing the pump power and carefully adjusting the intra-cavity PCs, we have obtained bound states of two parabolic pulses. These bound states of parabolic pulses are separated by 6.5 ps. Through changing pump power and orienting the polarization controllers, our laser can operate in different states with three, four and five bound pulse operation.3. We have developed a theoretical treatment for the normal-dispersion optical cubicon fiber amplifier with an arbitrary longitudinal gain profile and with constant gain profile. The expressions of phaseφ( z ,τ), chirpδωand amplitude A( z,τ) of such amplifier are found analytically when the nonlinear phase shifts and the third order dispersion (TOD) are all included. The results showed that the characteristics of self-similarity and linear chirp are lost due to third order dispersion.4. Using the standard split-step Fourier method, we have also simulated the asymmetric pulse propagation in the compression fiber, and have found that for a definite TOD, there exists an optimal nonlinear phase, in which value, the optimal compression pulse can has a higher peak power.